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Scientists are rethinking how we get Valley fever after new data from air monitoring

By Mark Brodie
Published: Monday, February 19, 2024 - 11:52am

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New data suggest some of what we thought we knew about how Valley fever spreads is not, in fact, true.

The study was published in Scientific Reports, and is based on data gathered from air filters set up in some of the country’s biggest cities after 9/11. They were intended to be used to monitor potential biothreat agents in the air, and while they haven’t detected any of those, they have been gathering information scientists hadn’t been looking at until now.

Dr. Dave Engelthaler is one of those scientists. He's the director of the Infectious Disease Arm of the Translational Genomics Research Institute, or TGen, and joined The Show to discuss the issue.

Valley fever coccidioides fungus
Pooja Gandhi/Centers for Disease Control and Prevention
Medical illustration of coccidioides, the fungus that causes Valley fever (coccidioidomycosis).

Full interview

Dave, some of the information from these filters has to do with the fungus that causes Valley fever, and it seems as though some of what you’re finding is maybe a little counter-intuitive?

DAVE ENGELTHALER: Yeah, exactly. I've, I've definitely wanted to be able to look at, Valley fever where people are getting exposed to the fungus and that is in the air and we haven't had that ability really until now. And, and using these air filters, we can look at when the Valley fever fungus, what we call cocci, shows up in the air, where it shows up, for how long, and then also might, what might be causing that, which we think is really important to help prevent cases into the future.

Yeah. So what do we know now based on this new information about what might be causing cocci to be up in the air?

ENGELTHALER: Yeah, I think that, you know, we started to build out the story without having really good information beforehand. And that included thinking that dust storms or these haboobs are really important cause of Valley fever. And what we're finding is that they're not. There, in fact, seem to have no significant effect actually, of people getting exposed to the Valley fever fungus. We're also seeing that the fungus when the, the fungal spores are in the air, it's not uniformly distributed. You don't see it across the Valley all the time. We'll see, tend to see hotspots showing up, and then going away. And so it, it seems like maybe it's, it's a lot more variable and a lot more locally focused than we had originally thought.

Does it seem as though there's any rhyme or reason to where those hotspots pop up and, and when and why?

ENGELTHALER: Yeah, we think that really what's important is just kind of going back to the basic life cycle of this fungus, which is the fungus has to, is growing in the soil, in, in a specific location. And then that soil is contaminated, it gets disturbed and the spores can get up into the air and then somebody or, or a dog or some animal, has to breathe it in to, to continue that life cycle of, of infection. And then it's got to get back into the soil at some point. And so what's really important is that we know that the soil is not uniformly contaminated.

And so it has to be where the fungus is in the soil that gets disturbed. And we think that happens on a much more local level than say, for instance, a giant dust storm blowing through and pushing contamination or con the fungus up into the air.

So would the key then be or maybe a key in somehow figuring out where in the soil, this fungus is living like if it's in this part of town or on this lot or in this part of the desert, if we were able to know that, would that be helpful in trying to maybe direct people not to go in those areas at particular times?

ENGELTHALER: Yeah, I think that's a really important point, Mark, but we also wanna make sure then that if wherever we have it in the soil, we're not causing it to get up into the air for people to breathe in. And so really what we know about the soil is that it is highly variable. When it shows up, you could have a real hot spot in the soil, say where an animal burrow was, maybe an animal had died with the fungus and it contaminated the soil, but you could go just a few feet away and dig up and not find the fungus right there.

So it is very spotty and, and really variable, variably dispersed around the endemic area of the Southwest. We do know that it, it, it does occur in the soils throughout the Valley region and the surrounding desert. So where there may be disturbances like new construction or new development or even people just gardening in an area where the fungus had existed, could cause those spores to come up out of the soil and into the air and then we breathe it in.

So we think this is what we're seeing now, is this very localized effects that are occurring probably 1,000 times a day in neighborhoods all over the Valley. And then you just accidentally are gonna get exposed to those spores versus saying this broad based contamination of the, of the air in Phoenix, which doesn't seem to be the case at all.

Yeah. Well, like is there any way to be able to tell if a particular plot of soil has this fungus in it? Like, is there a way to detect that?

ENGELTHALER: It's really tough to do. And, and it's, it's not easy to detect the fungus in the soil, but we can. And it, it probably doesn't make sense to try to find out every place it is because like I said, you could have it in one location and then just a few feet over it not be there. So just do a random soil sampling probably doesn't tell us much, but maybe what we can do is more soil sampling in areas where we know we're going to disturb a lot of soil, so like new development, turning over an ag field into condominiums. That might actually be useful, or at least if that is occurring, better ways to mitigate and prevent that soil from getting up into the air.

We, we already do a lot of dust mitigation. There may have to be more based off of the findings that we have and, and the continued studies that we're doing.

How much more difficult does it make your job in trying to learn about this and trying to figure out maybe where these spores exist and, and how they get kicked up into the air, when the majority of people who have these spores inside them will never show symptoms of Valley fever?

ENGELTHALER: That's a really good point. We know that there's a lot of exposures that happen. In fact, CDC estimates over 300,000 infections every year in the Southwest, and the vast majority of those people don't even know they have it. Maybe they just have a mild upper respiratory disease or respiratory disease, maybe they have walking pneumonia, and then some small fraction goes into the health-care system, and some fraction of that actually gets tested and shown to, to have Valley fever. So we, we can't understand valley fever just by looking at human cases, which is really what we've been doing for the last 50 years, trying to understand this by just looking at what cases show up.

Now, what we have is the tools to look at it better in our environment and see where is it showing up? How is it moving, what might be driving that to happen? Therefore, we can have much more targeted, better resolution with our public health messaging and response efforts.

Yeah. So given this new tool and maybe a slightly more precise way of, of knowing where cocci is. What kinds of steps do you think that public health officials and maybe residents should be taking given this information?

ENGELTHALER: I think you know, we're working really closely with local and state public health as well as the Centers for Disease Control and with National Weather Service and Homeland Security to better understand what this data is telling us and how we can use it. Right now, we're starting to map it more closely to where we know people are becoming infected. We're also mapping it closer but using satellite imagery to see what is happening in the the immediate surrounding areas before and during the time that filters become positive, so that we can have again that higher resolution on what is really driving the fungus getting up into the air.

This is a moving target, and we finally have the tools actually to be looking at this more closely.

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